1. Field of the Invention
The present invention relates to a display device including an organic resin film and in particular to a connection structure for mounting a driving circuit (driving IC) on the periphery of a display region.
2. Description of the Related Art
For example, a display device using liquid crystal includes two insulating (for example glass) substrates with liquid crystal sandwiched therebetween and a driving IC connected to the end of the insulating substrates, the insulating substrates arranged on a planar light source device called a backlight. For example, in a liquid crystal display device using a thin-film transistor (TFT), thin-film transistors are arranged in a matrix shape on one substrate (TFT array substrate) out of the two insulating substrates and the substrate is overlaid on the other substrate (CF substrate) with the external shape protruding beyond the same. Further, in the case of a reflective or semi-transparent type liquid crystal display device, a reflection electrode layer composed of an organic resin film is formed to form a reflection electrode including asperities on a TFT array substrate. Each TFT includes a pixel formed thereon. An image signal transmitted to a pixel is controlled by turning ON or OFF the TFT. Source wiring for inputting an image signal from the source electrode of each TFT is drawn to the end of a glass substrate. Near the end of the TFT array substrate is formed a pad (connection terminal) for connecting a driving IC. The inorganic insulating film layer is removed from the surface of the pad and a transparent conductive film is formed on the exposed source wiring material.
Gate wiring for turning ON/OFF the TFT is drawn from the gate electrode of each TFT to the end of the TFT substrate. Near the end of the TFT array substrate is formed a pad (connection terminal) for connecting a driving IC, same as the source side. For example, in a configuration where a driving IC is mounted by a flip-chip mounting method, a driving IC is directly mounted on the connection terminal in a mounting region arranged in a portion where the TFT array substrate at the panel end is protruding by way of an adhesive resin including conductive particles dispersed therein called ACF (anisotropic conductive film). At the end of the wiring arranged near the driving IC on the TFT array substrate closer to the end the TFT array substrate is formed a pad. To the pad is connected an FPC (flexible printed circuit board) via an ACF. The FPC is connected to a circuit board for controlling a driving IC. A control signal and a power for the driving IC are inputted to the driving IC via the wiring on the FPC and the wiring on the TFT array substrate. There may be a case where a driving IC is directly connected to a terminal formed on a TFT array substrate instead of an FPC.
In the related art, an example of a driving IC connecting structure of a liquid crystal display device using an organic resin film such as a reflective type liquid crystal display device does not form an organic resin film in the connecting portion of a driving IC and covers its surface with an inorganic insulating film layer alone (for example, refer to JP-A-2000-171817 (FIG. 2)).
With the driving IC connecting structure in the related art, it is necessary to provide a larger region where an organic resin film is removed than a region where an inorganic insulating film is removed in order to form a connection terminal on an insulating substrate. Thus, it is necessary to separately provide a process for removing an organic resin film and a process for removing an inorganic insulating film. This adds to the number of manufacturing processes and manufacturing costs. Another approach is to remove an organic resin film and an inorganic insulating film broadly over the periphery of a driving IC by using the same mask. In case this method is used, all the metallic wiring is exposed in a portion where the organic resin film and the inorganic insulating film are removed, resulting in reduced insulating properties between wires or corrosion of wiring. Another approach is to remove only the connection terminals of an organic resin film and an inorganic insulating film at the same time by using the same pattern. This method presents a problem that the bonding strength between the anisotropic conductive film for connection and the organic resin film is lower than that between the anisotropic conductive film and the inorganic insulating film thus reducing the connection reliability.